The overall goal of this multi-phase SBIR research effort is to create a PDA-based instrument for the comprehensive assessment of chronic pain (i.e., the location, quality, intensity, distress, interference, and beliefs dimensions) that offers improved accuracy and efficiency over conventional approaches. The KnowPain assessment instrument will be able to provide reliable and valid ratings of pain with significant reduction in both the required number of questions and assessment time. Existing multidimensional chronic pain assessment protocols often require an hour or more to complete. Item response theory (IRT) and computerized adaptive testing (CAT) are the key technologies that will enable more accurate and efficient administration of pain questionnaires. Multivariate IRT (MIRT) will be used to perform a statistical study of questionnaire item performance as it relates to the underlying respondent traits. All necessary tests of IRT assumptions, item calibrations, assessments of model fit, and differential item functioning will be performed. The MIRT analyses will result in a calibrated bank of pain assessment items that will be utilized by the CAT-driven KnowPain instrument to optimize the efficiency of pain assessment via administration of a minimum number of appropriate items. The KnowPain assessment instrument will be tested with human subjects in a validation trial against conventional measures. The accurate assessment of pain is an important goal; the first decade of the new millennium has been declared the "decade of pain control and research". As further support, the Joint Council on Accreditation of Healthcare Organizations (JCAHO) has declared pain the 5th vital sign. Products resulting from this research are anticipated to offer a great benefit to the field of pain assessment. Current pain assessment questionnaires are often time consuming to fill out. A device, such as the KnowPain instrument, that offers an adaptive set of pain assessment questions will not only reduce the time involved with current pain assessment methodologies, but also provide more accurate results and be more appealing to patients and clinicians. [unreadable] [unreadable] [unreadable]